Record receiver having plural interactive leaves or a colorless – Having a colorless color-former – developer therefor – or... – Method of use – kit – or combined with marking instrument or...
Reexamination Certificate
2000-03-02
2003-04-08
Hess, Bruce H. (Department: 1774)
Record receiver having plural interactive leaves or a colorless
Having a colorless color-former, developer therefor, or...
Method of use, kit, or combined with marking instrument or...
C503S226000
Reexamination Certificate
active
06544925
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to an indicator system which is responsive at a temperature-dependent rate to yield a visually-distinct indication of cumulative thermal exposure of an associated product in excess of a predetermined time-temperature integral. More particularly, the invention relates to such a system which is attached to a unit of thermally-sensitive perishable product and is activated at the time of introduction of the unit into commerce to initiate the monitoring of the unit's cumulative exposure to harmful temperatures. The system provides for the generation of a visually-distinct color which signals the end-point of the safe, useful shelflife of the product when the allowable time-temperature integral is exceeded. In a preferred embodiment, the indicator system of the invention comprises the use of a direct thermal label paper and an additional element which is applied to the label to react therewith and initiate a time- and temperature-dependent color change useful in monitoring the cumulative ambient temperature exposure of a labeled perishable product.
Color-forming or color-changing temperature-sensitive indicators which are capable of monitoring the handling of perishable goods are generally known and their use for this purpose is increasing. The utility of such indicators is to signal when a perishable article to which the indicator is attached has reached the point of quality loss, or unsafe condition, due to periods of excessive temperature exposures after which the product should no longer be used, or the product should be closely scrutinized to ensure suitable quality prior to being used. Indicator systems of this nature are important to ensure the quality and safety of perishable foods, pharmaceuticals, chemicals, and other such sensitive items.
In the case of perishable foods, modern packaging technologies are employed in an attempt to extend the shelf life of such products as meat, poultry, and fish. For example, plastic films with various gas permeabilities and barrier properties are used to maintain gas mixtures in the package to reduce the proliferation of aerobic spoilage organisms. However, the microbiology of food contained in this type of package permits anaerobic pathogens to grow in this modified gas atmosphere under suitable temperature conditions with no organoleptic sign of spoilage. A food product thus exposed to such temperature abuse can produce a lethal concentration of pathogens, yet provide no discernable sign of spoilage, a condition which can lead to serious health consequences if the product is consumed. It is therefore a safety feature for the consumer to have an indicator system associated with the perishable product in order to provide some visual indication that can warn of exposure of the product beyond an acceptable combination of time and temperature, i.e. a critical “time-temperature integral”.
With respect to highly perishable foodstuffs, e.g., meat, poultry, and fish, it is advantageous for the indicator system to be placed on each unit of sale so that continuous monitoring is carried out from the time of packing until the time of use. Otherwise, there would be no indication that a packaged product has been subjected to an unknown temperature excursion, such as could result during transportation and distribution or from intermittent customer handling or removal from a refrigerated case, which could lead to significant quality degradation and health endangerment.
In order to be most effective, indicator systems should be formulated and employed to provide a visual indication, such as a change in color, contemporaneously with the generation of conditions of spoilage in the associated perishable products. To this end indicator systems should ideally have a rate of visual change paralleling the deterioration rate of the associated product. Although such an ideal performance is not readily achievable in view of the myriad conditions influencing product spoilage, indicator systems should at least be operable only during their association with a product. That is to say, an effective indicator system should not be susceptible of responding to or registering temperature gradients to which it has itself been exposed between the time of its own manufacture and the time it is ultimately attached to the intended perishable product. Only in this manner is an indicator system able to reliably monitor the complete thermal history of an associated perishable product throughout the various phases of that product's storage and distribution.
In earlier attempts to meet the need for independent response in time-temperature indicator systems, such as freeze/thaw monitors and shelflife markers, the indicator product, in the form of label, tag device, or the like, was isolated from actinic temperatures immediately upon manufacture, such as by freezing or at least cooling to a non-active temperature. For example, widely-used labels comprising diacetylene monomer inks registering irreversible color generation upon polymerization as a function of ambient temperature were required to be stored from the time of manufacture at temperatures below the threshold of significant color-forming polymerization. Such expedients were effective as long as storage and handling conditions were scrupulously monitored; however, these indicator system products were themselves subject to the same vagaries of human behavior as were the perishable products they were intended to protect, and the desired reliability could be compromised. The expenditure, albeit occasionally futile, of equipment and resources in an attempt to ensure the required storage conditions sometimes outweighed the initial cost of the indicator product.
Thus, apart from the fundamental requirements of reproducibility and economical production, an acceptable indicator system must be isolated in an economical and “fail-safe” manner from conditions which would otherwise initiate its own temperature response reaction and detract from its ability to register a true time-temperature integral vis-a-vis a given perishable product with which it is ultimately to be associated. The most reliable such means for isolation is to formulate or configure the indicator system to be in an inactive state which is made active only at the time of its association with the product unit to be monitored. The present invention provides such an economical, reliable, and activatable time-temperature indicator system.
A number of activatable time-temperature indicator systems have previously been proposed, yet none provides a ready and economical means for preventing premature initiation of the underlying temperature-sensitive indicator reaction. In a majority of such systems which comprise, for example, a label which is to be affixed to a perishable product, potential co-reactant components, such as precursors to an ambient temperature color-forming reaction, are located in close proximity, as in contiguous layers or interspersed mixtures, yet are maintained in reactive isolation by means of additional intervening layers, encapsulating films, or the like. Each of such isolating means, however, introduces additional expenses of resources and manufacturing operations. Further, these indicator products continue, due to the close proximity of potential reactants, to be susceptible to inadvertent, premature activation, such as where pressure-rupturable isolating encapsulations are subjected to mishandling or dormant light-sensitive co-reactants experience vagrant actinic exposure, or where other acceptable storage conditions are exceeded.
Another consideration which has contributed to the limited acceptability of currently-available activatable indicator systems is the excessive economic expenditures in materials and manufacturing operations resulting from the requirement for indicator and activating compositions or means to be individually formulated and assembled, along with isolation means, into the final composite indicator system product. Thus, from the viewpoint of economical accepta
Arnold Raymond M.
Piechowski Allan P.
Prusik Thaddeus
Hess Bruce H.
LifeLines Technology, Inc.
White Lionel N.
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